1. Field of the Invention
This invention relates to a lens barrel to be used while collapsing a lens group in one aspect and while extending the lens group to predetermined positions in another aspect. More specifically, this invention relates to a lens barrel suitable for a zoom lens capable of changing a focal length by relatively moving multiple lens groups, and also relates to a camera, a portable information terminal device, and an image input device.
2. Description of the Related Art
In terms of an image-taking apparatus such as a digital camera, along with higher performance of image-taking lenses such as zoom lenses and progress in miniaturization required by users, there is a growing demand for an image-taking lens of a retractable type configured to collapse a movable lens barrel into a camera main body when no image is taken.
In addition, due to an increasing demand for a thin camera main body (an image-taking apparatus), it is deemed important to minimize dimensions of a movable lens barrel in a direction of an image-taking optical axis when the lens barrel is collapsed and housed.
To meet such a demand for a thin camera main body, Japanese Patent Application Laid-open Publication Nos. 2003-315861 and 2003-149723 disclose techniques for displacing at least part of lens groups away from an image-taking optical axis when collapsing and housing a movable lens barrel into a camera main body.
According to these techniques, some of the lens groups are displaced away from the image-taking optical axis when housing the movable lens barrel. Therefore, it is possible to minimize dimensions of the movable lens barrel in a direction of an image-taking optical axis, and thereby to achieve a thin camera main body (a main unit of an image-taking apparatus)
However, according to the techniques disclosed in Japanese Patent Application Laid-open Publication Nos. 2003-315861 and 2003-149723, a retracting position of the lens group away from the image-taking optical axis is virtually located within a maximum outer diameter of a fixed barrel of the camera main body. Therefore, these conventional techniques can reduce dimensions in the direction of the image-taking optical axis when the movable lens barrel is housed, but causes an increase in the outer diameter of the fixed barrel. Hence these techniques have inconvenience that the size of the fixed barrel becomes relatively large when the camera main body (the image-taking apparatus) is viewed from a front side (from an object's side).
Accordingly, there has been disclosed a lens barrel configured to change from a collapsed state, in which at least part of multiple lens groups is collapsed to be housed in a main body, to an image-taking state, in which at least part of the lens groups is moved toward an object. This technique provides the lens barrel including multiple lens holder frames each configured to hold each of the multiple lens groups, a movable lens barrel configured to hold the lens holder frames inside, and lens holder frame driving means for driving the lens holder frames through the movable lens barrel. Here, in the image-taking state, the lens holder frames are configured to locate all the lens groups on an image-taking optical axis. On the other hand, in the collapsed state, the lens holder frames are configured to allow at least one lens group to retract into a position away from the image-taking optical axis, and to retract outside a maximum outer diameter of the movable lens barrel of another lens group. For this reason, the lens barrel includes a retracting lens holder frame configured to hold and move the two lens groups.
In this lens barrel, a cam is formed on the retracting lens holder configured to hold the retracting lens group in order to move at least part of the lens groups into the image-taking optical axis, to allow part of the lens group to retract away from the image-taking optical axis, and to move the lens group along the image-taking optical axis at the time of image-taking. Here, the cam has a shape capable of moving the retracting lenses to an image-taking position, and to a housed position by use of a retracting lens holder frame driving pin.
However, if a drop impact or the like is applied to the camera main body (a main body of an image-taking apparatus) when the retracting lens holder frames are located in the retracting position, the retracting lens holder frames and the retracting lens holder frame driving pin may be disengaged from the cam and normal drive may be disabled thereafter. Hence there has been a risk of inconvenience that it is not possible to recover the normal state unless the camera is overhauled.